Etymology: < classical Latin lacerta (also lacertus) lizard, of unknown origin; perhaps an extended use of lacertus upper arm (see lacert n.²), although it is more likely that the latter is an extended use of the former (see semantic parallels cited at lacert n.²). Compare lizard n., which ultimately reflects the same Latin etymon.

Etymology: < (i) Middle French lacert, lacerte muscle (1314 in Old French; French †lacerte ), and its etymon (ii) classical Latin lacertus upper arm, in post-classical Latin also muscle (a1250 in a British source), perhaps an extended use of lacertus lizard; compare classical Latin musculus muscle, lit. ‘little mouse’ (see muscle n.), ancient Greek μῦς mouse, muscle (see myo- comb. form).Proposed cognates in other Indo-European languages (e.g. Byzantine Greek λικερτίζειν ‘to jump, dance’) support a primary sense of 'upper arm' but if the two Latin words are identical, a transfer of sense from ‘lizard’ to ‘upper arm’ is more plausible than the reverse.