'whimsically-decided' originates from the combination of 'whimsical' and 'decided'. 'Whimsical' comes from the word 'whimsy', which has roots in the 17th century, meaning 'fanciful or capricious'. 'Decided' is derived from the Latin 'decidere', meaning 'to cut off' or 'determine'.

'Whimsical' evolved from 'whimsy', which was used in the 17th century to describe fanciful notions. 'Decide' has been used since the 14th century, evolving from the Latin 'decidere'.

Initially, 'whimsical' meant 'fanciful or capricious', and 'decide' meant 'to determine'. Together, they convey a decision made in a fanciful manner.