similar: [17] Similar comes via French similaire from medieval Latin *similāris, a derivative of Latin similis ‘like, similar’. This or the closely related simul ‘at the same time’ have also given English assemble [13], dissemble [15], ensemble [15], resemble, semblance [13], similitude [14], simulate [17], and simultaneous [17]. Its ultimate source was the Indo-European base *sem-, *som-, which also lies behind English same, simple, single, and the homo- of homosexual. => assemble, dissemble, ensemble, resemble, same, semblance, simple, simulate, simultaneous, single
similar (adj.)
"having characteristics in common," 1610s (earlier similary, 1560s), from French similaire, from a Medieval Latin extended form of Latin similis "like, resembling," from Old Latin semol "together," from PIE root *sem- (1) "one, as one, together with" (see same). The noun meaning "that which is similar" is from 1650s. Related: Similarly.