Origin of joistMiddle English giste from OFr, a bed, couch, beam from gesir, to lie from Classical Latin jacere, to lie, throw: see jet
transitive verbjoist·ed, joist·ing, joists
Origin of joistMiddle English giste, joiste from Old French giste from feminine past participle of gesir to lie, lie down from Latin iacēre ; see yē- in Indo-European roots.
(third-person singular simple present joists, present participle joisting, simple past and past participle joisted)
Old French giste, feminine of gist, the past participle of gesir (“to lie down”).