Quote:

Does the OED or whatever source you're using say why Ucalegon means generally 'a neighbour whose house is on fire' rather than it being the name of a neighbour whose house was on fire?





#667. [Source of danger.] Pitfall
-- N. rocks, reefs, coral reef, sunken rocks, snags; sands, quicksands; syrt|, syrtis|; Goodwin sands, sandy foundation; slippery ground; breakers, shoals, shallows, bank, shelf, flat, lee shore, ironbound coast; rock ahead, breakers ahead. precipice; maelstrom, volcano; ambush &c. 530; pitfall, trapdoor; trap &c. (snare) 545. sword of Damocles; wolf at the door, snake in the grass, death in the pot; latency &c. 526. ugly customer, dangerous person, le chat qui dort; firebrand, hornet's nest.
Phr. latet anquis in herba [Vergil]; proximus ardet Ucalegon [Vergil].
-Roget's Thesaurus

as ASp suggested, it's eponymous, first used specifically by Juvenal and others (see the link in the original post above); and then alluded to a bit more generally. OED has two citations where this is shown:

1849 DE QUINCEY Eng. Mail Coach Wks. 1862 IV. 297 Ucalegon, as it happened, was not in the way-bill and therefore could not have been booked. [under way-bill]

1910 W. G. COLLINGWOOD Dutch Agnes 182 But proximus ardet Ucalegon, which is to say, ‘Don't care's house is afire, and his neighbour is quaking.’ [under neighbo(u)r]

The former doesn't make much sense taken out of context; here's a link to Thomas de Quincey's The English Mail-Coach and Joan of Arc which lends some droll humo(u)r to the passage.

but, to your point, I'd wager that ucalegon, when used, has always been capitalized. oops. well, that could have given away the game, although we would have probably had a bunch of paedia type entries to choose from.

try Google[Books] -- there are 66 works listed with the phrase proximus ardet Ucalegon, some with no further gloss at all; i.e., it is used as a warning. There are 278 (listed) works that contain "ucalegon".

to wit, from Gargantua and Pantagruel:
Cheer up, cried out Pantagruel; cheer up, my boys; let us be ourselves again. Do you see yonder, close by our ship, two barks, three sloops, five ships, eight pinks, four yawls, and six frigates making towards us, sent by the good people of the neighbouring island to our relief? But who is this Ucalegon below, that cries and makes such a sad moan? Were it not that I hold the mast firmly with both my hands, and keep it straighter than two hundred tacklings—I would—It is, said Friar John, that poor devil Panurge, who is troubled with a calf's ague; he quakes for fear when his belly's full.

-joe (SAWH* : ) bfstplk

*Society of Apologists for Wrong-headed Hogmasters

p.s. - In the glossary for 'The Aeneid', it is indicated that the name Ucalegon means "Not caring". (see Collingwood citation?)