From Old English 'bycgan,' a distinctly Germanic word with no certain cognates outside the family.
To obtain something in exchange for payment; to purchase.
From Old English 'bycgan' meaning 'to buy, pay for, acquire,' from Proto-Germanic *bugjaną (to buy), of uncertain further origin. Some scholars link it to Gothic 'bugjan' and suggest a connection to PIE *bʰewgʰ- (to bend), with the semantic development passing through 'to bend' → 'to turn over in exchange.' The word replaced the earlier Proto-Indo-European root
The past tense 'bought' is one of the most irregular in English — Old English 'bycgan' had a suppletive past tense 'bohte,' and the dramatic difference between 'buy' and 'bought' reflects a prehistoric pattern where the present and past stems were formed from different ablaut grades of the same root.