'blossom' originates from Old English, specifically the word 'blōstm' (also written 'blóstma'), where the root 'blōs-' meant 'bloom' or 'flower'.

'blōstm' came from Proto-Germanic '*blōstmaz' and passed into Middle English as 'blossom', eventually becoming the modern English word 'blossom'.

Initially it meant 'a flower or mass of flowers'; over time the word kept that literal sense and extended figuratively to mean 'to develop, flourish'.