'praisingly' is formed in modern English from the verb 'praise' + the present-participial/adjectival suffix '-ing' + the adverbial suffix '-ly'. 'praise' itself comes into English via Old French from Latin-related roots.

'praise' entered Middle English as 'preisen' / 'praisen' from Old French (e.g. 'preisier'), which in turn is connected to Latin 'pretium' (meaning 'price' or 'value'); from 'praise' the forms 'praising' and then 'praisingly' were derived in later English by adding '-ing' and '-ly'.

Originally related to valuing or esteeming (from roots meaning 'price' or 'value'), the sense shifted to expressing approval or commendation; 'praisingly' now means 'in a manner that expresses praise or approval.'