late 14c., pleiten, "to fold (something), gather in pleats, double in narrow strips," also "to braid or weave (something)," from plait (n.) and also from Old French pleir "to fold," variant of ploier, ployer "to fold, bend," from Latin plicare "to fold" (from PIE root *plek- "to plait"). Related: Plaited; plaiting.
late 14c., pleit, "a fold, a crease, a flattened gather made by doubling cloth or similar fabric in narrow strips upon itself," also "interlaced strands of hair," from Anglo-French pleit, Old French ploit, earlier pleit, "fold, manner of folding," from Latin plicatus, past participle of plicare "to lay, fold, twist" (from PIE root *plek- "to plait").
"to fold or gather in pleats," 1560s, used as the verb version of plait (n.) and probably representing an alternative pronunciation. Related: Pleated; pleating.
"a fold," 1580s, variant of plait (n.). With a gap in the printed record 17c.-18c., but according to OED probably it was in continuous oral use. Compare the verb.
late Old English pliht, "danger, harm, trouble; strife," from Anglo-French plit, pleit, Old French pleit, ploit "condition" (13c.), originally "way of folding," from Vulgar Latin *plictum, from Latin plicitum, neuter past participle of Latin plicare "to fold, lay" (from PIE root *plek- "to plait"). A doublet of plait (n.).
Originally "condition or state," usually "a bad condition or state" but sometimes in a neutral sense (as in modern French en bon plit "in good condition"); the predominant sense of "harmful state" (and current spelling) probably is from convergence and confusion with plight (n.2) via a notion of "entangling risk, pledge or promise with great risk to the pledger."
It forms all or part of: accomplice; application; apply; complex; complexion; complicate; complication; complicity; deploy; display; duplex; duplicate; duplicity; employ; explicate; explicit; exploit; flax; implex; implicate; implication; implicit; imply; multiply; perplex; perplexity; plait; plash (v.2) "to interlace;" pleat; -plex; plexus; pliable; pliant; plie; plight (n.1) "condition or state;" ply (v.1) "work with, use;" ply (v.2) "to bend; ply (n.) "a layer, fold;" replica; replicate; replication; reply; simplex; splay; triplicate.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit prasna- "turban;" Greek plekein "to plait, braid, wind, twine," plektos "twisted;" Latin plicare "to lay, fold, twist," plectere (past participle plexus) "to plait, braid, intertwine;" Old Church Slavonic plesti "to braid, plait, twist," Russian plesti; Gothic flahta "braid;" Old Norse fletta, Old High German flehtan "to plait;" Old English fleax "cloth made with flax, linen."