'azimuthally' originates ultimately from Arabic, specifically the Arabic phrase 'al‑samt' (السمت) / 'samt' meaning 'direction'.

'azimuthally' developed via the noun 'azimuth' (Medieval Latin/Old French/Spanish forms like 'azimut' derived from Arabic 'al‑samt'), then the adjective 'azimuthal' was formed in English, and the adverb was made by adding the suffix '-ly' to produce 'azimuthally'.

Initially the root meant 'direction' in Arabic; over time the term became specialized in European languages for the horizontal angular direction used in astronomy and navigation, and 'azimuthally' now means 'in terms of or according to azimuth'.