'aneurismally' originates from 'aneurismal' (relating to aneurism), which comes from 'aneurism', itself from Greek 'aneurysma', where 'ana-' meant 'up' and 'eurys' meant 'wide'.

'aneurysma' transformed into the Late Latin 'aneurysma', then into the French 'anévrisme', and eventually became the English 'aneurism' and its derivatives like 'aneurismal' and 'aneurismally'.

Initially, it meant 'relating to a widening or dilation (of a blood vessel)', and now it specifically refers to things characteristic of or relating to an aneurism.