Sometimes the changing spellings of surnames can tend to confuse us.
The first example is fairly obvious. The name Lidgey began life in the early 1600s in Redruth and on the Lizard (where it was more likely to be Ludgy). It doesn’t take a great deal of detective work to find the placename Lidgey at St Gluvias, spelt Lugie in 1613. Earlier, in 1342, this was spelt Lusy, the/s/ being pronounced /dg/ in Cornish by the later 1500s. (The placename is either from les, plant, or possibly lus, bilberries.) Sure enough, in the 1540s there was a John Lusye living at St Gluvias.
Lanxon is much more ambiguous. It’s been suggested that it comes from Lanson (the town). But it’s more likely to have originated in the English placename Langstone or Longstone. Admittedly, early spellings are ambiguous. Walter and William Lanston were found at Blisland and Camelford on the north west fringes of Bodmin Moor in 1543. While that might indicate they hailed from Lanson, there is also, significantly, a place called Langstone in the parish of Blisland. There were also folk called Langston or Langstone in various places in south-east Cornwall in the late 1500s and early 1600s, no doubt from another two places called Langstone to the east of Bodmin Moor.
During the later 1500s Langstone became the most common spelling and the variant Lanxon also emerged, both found in roughly the same two areas. However, while Langstone in the south east seems to have died out by the 1700s, Lanxon prospered in the district around Blisland. This strongly implies the modern Lanxons are likely to be able to trace their ancestry back to the place Langstone in Blisland.
Loam is the most puzzling of these three names. Its first appearance was not until the beginning of the 1700s in St Agnes. However, before that date several people named Lome are found in the records. This was clearly the original spelling, but its meaning is not obvious. The geography of the surname before the mid-1600s doesn’t give us many clues but also doesn’t preclude a Cornish language origin. But what?
Cornish studies resources 
Just on loam, could it really be just that (regardless of older spelling)? I conducted research with farmers in Madagascar and one of my respondents was called ‘Manure’ – his friends laughed when he said his name, but clearly it was a good farmer’s name, too.
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PS a private matter – I live at the Rookery Warleggan and have been conducting quite a lot of research into the religious radical Ralph de Tremur and his uncle John de Tremur (much less research on him, Ralph is the very interesting one because he preceded the Lollards by decades and perhaps counts as the very first ‘protestant’ in the UK or the world! Perhaps exaggeration. I can share my research at some point with you but would love to more about the de Tremurs. I understand they were south coast folks probably around St Austell, and that Tremur = mere (marsh etc) but perhaps you know much much more.
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Hi Cathy, Your research sounds most interesting. The placename Tremur was a variant spelling of Tremear (tre+meur). The element meur doesn’t have anything to do with Old English mere but is Cornish for big or large, thus great or large farmstead as opposed to little or lesser farmstead. It was a very common placename, with at least 11 examples across Cornwall. Those in the east (at St Ive, St Clether, Lanivet, Lanteglos by Fowey and St Tudy) were later spelt Tremear or Tremeer. Those further west (at Sennen, Merther, St Merryn, St Issey, Gorran and St Stephen in Brannel) were spelt Treveer or similar, reflecting the correct grammar. As such there were probably multiple origins for the surname. In the early 1500s it appeared (as Tremere/Tremure/Trevere) at Sennen, Merther, St Buryan, Breage, Egloshayle and St Teath, which distribution bears that out. Ralph de Tremure’s family could have been from any of those 11 places. The earliest de Tremur in my notes is William, who had land at St Kew in 1328, while in the 1400s his heirs had land in St Columb Minor, which may suggest a mid-Cornwall origin.
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Maybe also for Lidgey: although 15C Bewnans Ke has a few stanzas on Oubra gathering herbs and in line 1165 the word was spelt losow, E Lhuyd from the 17C vernacular (Archæologia Britannica page 243 column a para 4) has Lozouez and Lẏzẏuyz for herbs. (A possible herbal link with Letcher might also be pondered.) That possible s>dg from losow from might also fit the St-Just-in-Penwith place name Letcha (Lesse in 1327, then Lasshe in 1340, Lessa in 1536 and Lecha in 1589, from JEB Gover’s list).
For Loam, another cornuphone placename or byname possibility, though b > bm pre-occlusion might have been expected (though not found in W Borlase’s 18C *Lommen, a Mess; *lommen *coul, a Mess of Pottage.): as with Moyle / bare|bald e.g. Mulfra/Melbur/Mulberry/Moelfre/Malvern / bare hill, perhaps lomm / droplet/smooth e.g. Top Lobm as e.g. transient Snives toponym in R M-Nance’s dictionary.
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