Where does the word originate?

C19 US. Perhaps from 'shin' and 'dig'. In the C19 it once meant a dig in the shins. The use of it for a lively country dance (also C19) would seem to follow

'"dance, party, lively gathering," 1871, probably from shindy "a spree, merrymaking" (1821), perhaps from shinty, name of a Scottish game akin to hockey (1771), earlier shinny (see shinny (n.)).' www.etymonline.com

Thanks

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'Gaelic sinteag,”a leap”' au.encarta.msn.com

The OED finds no connection between the Scots game shinty and the word shindig. Shinny is another name for shinty, the game, and shindy is a dialect name for it.

The OED says that shindig " a (country) dance;a party; a lively noisy gathering" has been influenced by the word 'shindy', in another of its meanings (and the one it has in British English) " a commotion; a brawl".That dates from the C18. Shindig is not found until the C19. ( We say " to kick up a shindy" for " to make a big fuss about something, to cause a disturbance, make a commotion"). It says that shindig itself was a originally a 'dig in the shins',so perhaps literally from shin and dig [as above]

The explanation here mentions all of the above - www.worldwidewords.org