The story
Possibly a Western US English dialectal word of unknown origin. First attested in the early 19th century. Perhaps from contrive + trap + -tion, while also possibly approximating construction. Chambers suggests contrivance + adaption. Neither Chambers nor Concise Oxford suggests a US origin. Compare cantrip, cantrap (Scots dialect), a wilful piece of trickery.
Etymology from Wiktionary, CC BY-SA 4.0.