To a moderate degree; reasonably but not extremely. In a just or unbiased manner according to rules or standards.
From Old English 'fæger' (beautiful, pleasant) which evolved into 'fair' meaning both 'beautiful' and 'just.' The adverb form developed in Middle English, with the 'moderately' sense emerging from the idea of balance and proportion.
The dual meaning of 'fairly' (moderately and justly) reflects an ancient philosophical connection between beauty, balance, and justice - what the Greeks called 'kalos kagathos' (beautiful and good). Something done 'fairly' achieves the golden mean between extremes.
Complete word intelligence in one call. Free tier — 50 lookups/day.