the.com/sleigh bells

means Small hollow metal bells, often strapped to horse harnesses, that produce a bright jingling chime as the sleigh moves — originally a practical warning sound, now the shorthand jingle of holiday cheer.

from The bells themselves are old technology — crotal bells (the round, hollow, pea-in-a-cage kind) were used on horse and animal harnesses for centuries so people could hear a sleigh or cart coming on roads with no other warning, especially muffled by snow. 'Sleigh' itself comes from Dutch 'slee,' related to 'slede' (sledge), brought into English usage where snow travel by sled was common. The pairing of 'sleigh' and 'bells' as a fixed phrase owes much of its modern fame to 19th-century winter songs, which took a working farm sound and turned it into the jingling signature of Christmas.