Why “chose” in action? Why not “right/droit” in action?
Chose (in action)
this can be translated as ‘thing in action’. It is an intangible right which is essentially a right to sue.
JC Smith's The Law of Contract 2021 3 ed, p 476.
Cause comes via Old French cause from Latin causa, which as well as ‘reason’ meant ‘law-suit’; this was carried over into English legal language (it survives in terms such as cause-list ‘list of cases to be tried’) and its use in expressions like ‘plead someone’s cause’ led in the late 16th century to a more general application ‘goal or principle pursued or supported’. French chose ‘thing’ also comes from Latin causa, in the weakened sense ‘matter, subject’.
Word Origins (2005 2e) by John Ayto. p 99.