Etymologies from Etymonline.com:
"pledge," obsolete except in archaic plight one's troth, from O.E. pligtan "endanger," verb form of pliht "danger, risk," from P.Gmc. *pleg- (cf. O.E. pleon "to risk the loss of, expose to danger," O.Fris., M.Du. plicht "care, carefulness," O.H.G. pfliht, Ger. pflicht "obligation, duty," M.Du. plien "to answer for, guarantee").
"condition or state (usually bad)," c.1175, from Anglo-Fr. plit, O.Fr. pleit "condition" (13c.), originally "way of folding," from V.L. *plictum, from L. plicitum, neut. pp. of L. plicare "to fold, lay" (see ply (v.)). Originally in neutral sense (as in modern Fr. en bon plit "in good condition"), sense of "harmful state" is probably from convergence with plight (v.) via notion of "entangling risk, pledge or promise with great risk to the pledger."
As an aside, when I saw the German pflicht, I wondered whether this word may then be related also to the word conflict, which derives from Latin conflictus...
I also was intrigued by the relationship to pledge!