"Celtic monumental stone," 1768, from Welsh llech, cognate with Gaelic and Irish leac (see cromlech).
"yen, strong desire" (especially sexual), 1796, variant of letch. Meaning "a lecher" is by 1943.
"craving, longing," 1796, perhaps a back-formation from lecher, or from a figurative use of latch (v.) in a secondary sense of "grasp, grasp on to."
: when Henry goes letching after Anne/ keep Junior from leching (1911+)
[fr lecher, lechery, ultimately fr the notion of licking]