"quality of shining with a clear, soft light," 1817, from lambent (q.v.) + abstract noun suffix -cy. A figurative use, the etymological Latin sense "act or quality of licking" has been rare in English.
Entries linking to lambency
lambent adj.
of light, flame, etc., "flowing or running over the surface," 1640s, from a figurative use of Latin lambentem (nominative lambens), present participle of lambere "to lick, lap, wash, bathe," from PIE root *lab-, indicative of smacking lips or licking (source also of Greek laptein "to sip, to lick," Old English lapian "to lick, lap up, to suck;" see lap (v.1)).
-cy
abstract noun suffix of quality or rank, from Latin -cia, -tia, from Greek -kia, -tia, from abstract ending -ia (see -ia) + stem ending -c- or -t-. The native correspondents are -ship, -hood.