Etymology
Advertisement
lecher (n.)

"lustful man, man given to excessive sexual indulgence," late 12c., from Old French lecheor (Modern French lécheur) "one living a life of debauchery," especially "one given to sexual indulgence," literally "licker," agent noun from lechier "to lick;" also "to live in debauchery or gluttony," from Frankish *likkon or some other Germanic source, from Proto-Germanic *likkojan "to lick" (from PIE root *leigh- "to lick"). The Old French feminine form was lechiere. Middle English, meanwhile, had lickestre "female who licks;" figuratively "a pleasure seeker," literally "lickster," with -ster. In 18c. sometimes leacher (Bailey), along with leacherous, leachery.

Related entries & more 
Advertisement
lechery (n.)
"lewdness in living, habitual lustful indulgence," c. 1200, from Old French lecherie "gluttony, sensuality, lewdness," from lecheor "debauched man" (see lecher).
Related entries & more 
lecherous (adj.)

"prone to indulge in sensuality, lustful, lewd," c. 1300, probably from lecher + -ous; or else from rare Old French adjective lecheros. The nativized form is lickerish. Related: Lecherously; lecherousness.

Related entries & more 
letch (n.)
"craving, longing, strong desire," 1796 [Grose], perhaps a back-formation from lecher, or deformed from a figurative use of latch (v.) in a secondary sense of "grasp, grasp on to." Or perhaps from letch (v.), a variant of leach.
Related entries & more 
lech (n.2)
"yen, strong desire" (especially sexual and sometimes implying perversion), 1796, variant of letch, but according to OED "now regarded as a back-formation" from lecher. Meaning "a lecher" is by 1943. As a verb by 1911. Related: Leched; leching.
Related entries & more 
Advertisement
*leigh- 
Proto-Indo-European root meaning "to lick." It forms all or part of: cunnilingus; lecher; lichen; lick.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit ledhi "he licks," Armenian lizum "I lick," Greek leikhein "to lick," Latin lingere "to lick," Old Irish ligim "I lick," Welsh llwy "spoon," Old English liccian "to lick."
Related entries & more 
dirty (adj.)

"of or imparting filth," early 15c. metathesis of dritty "feculent; muddy" (late 14c.), from dirt + -y (2). Sense of characterized by dirt, unclean" is from 16c. Meaning "smutty, morally unclean" is from 1590s. Of colors, from 1690s. Sense of "not streamlined; rough, untidy, or imperfect" is by 1925. Of atomic bombs, "producing much radioactive fallout," by 1956.

Dirty linen "personal or familial secrets" is first recorded 1860s. Dirty work in the figurative sense is from 1764; dirty trick is from 1670s. Dirty joke is by 1856. The dirty look someone gives you is by 1923; dirty old man "superannuated lecher" is from 1932. Related: dirtiness.

Related entries & more 
lick (v.1)

Old English liccian "to pass the tongue over the surface, lap, lick up," from Proto-Germanic *likkon (source also of Old Saxon likkon, Dutch likken, Old High German lecchon, German lecken, Gothic bi-laigon), from PIE root *leigh- "to lick."

French lécher, Italian leccare are said to be Germanic loan words. The figurative lick (one's) lips in eager anticipation is from c. 1500. Lick-ladle (1849) was an old phrase for a (human) parasite. To lick (someone or something) into shape (1610s) is in reference to the supposed ways of bears:

Beres ben brought forthe al fowle and transformyd and after that by lyckyng of the fader and the moder they ben brought in to theyr kyndely shap. ["The Pylgremage of the Sowle," 1413]
Related entries & more 
lamia (n.)

female demon, late 14c., from Latin lamia "witch, sorceress, vampire," from Greek lamia "female vampire, man-eating monster," literally "swallower, lecher," from laimos "throat, gullet" (see larynx). Perhaps cognate with Latin lemures "spirits of the dead" (see lemur) and, like it, borrowed from a non-IE language. Used in early translations of the Bible for screech owls and sea monsters. In Middle English also sometimes, apparently, mermaids:

Also kynde erreþ in som beestes wondirliche j-schape, as it fareþ in a beest þat hatte lamia, þat haþ an heed as a mayde & body as a grym fissche[;] whan þat best lamya may fynde ony man, first a flatereþ wiþ hym with a wommannes face and makeþ hym ligge by here while he may dure, & whanne he may noferþere suffice to here lecherye þanne he rendeþ hym and sleþ and eteþ hym. [Bartholomew Glanville, "De proprietatibus rerum," c. 1240, translated by John of Trevisa c. 1398]
Related entries & more