'aslantwise' originates from English, specifically by combining the adverb 'aslant' and the suffix '-wise', where 'aslant' meant 'slanting' and the suffix '-wise' meant 'in the manner of'.

'aslantwise' developed from Middle English/Early Modern English adverbial formations that combined 'aslant' + '-wise' to create adverbial compounds; this pattern produced occasional rare forms such as 'aslantwise' which survived in limited literary or dialectal use.

Initially, it meant 'in a slanting manner', and over time it has retained that basic meaning (today it is rare/archaic and largely synonymous with 'slantwise' or 'obliquely').