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1640s, "tangled," from past participle adjective from complicate. Figurative meaning "not easy to solve, intricate, confused, difficult to unravel" is from 1650s.
1620s, "to intertwine" (as a past participle adjective, early 15c.), from Latin complicatus "folded together; confused, intricate," past participle of complicare (see complication). Meaning "to make more complex" is recorded from 1832, from earlier sense "to combine in a complex way" (17c.). Related: Complicated; complicating.