ludicer.

From lūdō (“play”). In terms of form, the neuter noun lūdicrum (“toy, plaything, public show”) could be interpreted as lūdō + -crum (instrument noun suffix); however, the adjective is attested earlier than the noun. Sen 2015 views this as compelling evidence that the noun was a later, secondary formation (by nominalization of the adjective), which is the generally accepted view; however, Moretti 2022 considers the chronology insufficient to rule out the possibility that the noun was formed first and gave rise to the adjective by reanalysis. In any case, the ending is probably ultimately derived from Proto-Indo-European *-tl-, a variant of the zero-grade of the agent suffix *-tḗr. Compare i-stem volucer, volucris and alacer, alacris.