Lewis & Short

1. lăbellum, i, n. dim. [1. labrum], a little lip, Plaut. Ps. 1, 1, 67; id. As. 4, 1, 52: dentes illidunt saepe labellis, * Lucr. 4, 1080: Platoni cum in cunis parvulo dormienti apes in labellis consedissent, Cic. Div. 1, 36, 78: nec te paeniteat calamo trivisse labellum, Verg. E. 2, 34; cf.: et roseo terit ore deus mollique labello, Pub. Syr. ap. Wernsd. Poet. L. Min. 2, 388: digito compesce labellum, Juv. 1, 160: extendere, to pout, thrust out, id. 15, 325: compara labella cum labellis, i. e. kiss, Plaut. As. 3, 3, 78.
As a term of endearment: meus ocellus, meum labellum, mea salus, meum savium, Plaut. Poen. 1, 2, 153; so id. ib. 1, 2, 175.