'partisanly' originates from English, specifically formed from the adjective 'partisan' plus the adverbial suffix '-ly', where 'partisan' ultimately comes from Old Italian 'partigiano' meaning 'supporter, adherent'.

'partisan' entered English from Middle French or directly from Italian (Old Italian 'partigiano'); the English adjective 'partisan' later took the productive adverbial suffix '-ly' to form 'partisanly'.

Initially related to being a 'member or follower' (often of a political party or faction), the term evolved to describe the quality of biased or factional support; 'partisanly' specifically denotes acting or speaking with that bias.