1590s, "a particular statement;" 1650s, "a proposition, assumed and taken for granted, used as a premise," from French hypothese and directly from Late Latin hypothesis, from Greek hypothesis "base, groundwork, foundation," hence in extended use "basis of an argument, supposition," literally "a placing under," from hypo- "under" (see hypo-) + thesis "a placing, proposition" (from reduplicated form of PIE root *dhe- "to set, put"). A term in logic; narrower scientific sense is from 1640s.
"founded on or characterized by a hypothesis, conjectural," 1580s, from Latinized form of Greek hypothetikos "pertaining to a hypothesis," from hypothesis (see hypothesis). Hypothetic (1670s) is less common. Related: Hypothetically.
1560s, "state or quality of being legally null and void," from French nullité (14c.) or directly from Medieval Latin nullitalis, from Latin nullus "not any" (see null). From 1580s as "a state of nothingness;" in reference to persons, "a non-entity," by 1650s.