E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A military punishment formerly practised; it consisted of pulling an offender to a beam and then letting him down suddenly; by this means a limb was not unfrequently dislocated. (Italian, strappare, to pull.)
Were I at the strappado or the rack, Id give no man a reason on compulsion.Shakespeare: 1 Henry IV., ii. 4.