经 here is the 'manual / classic' sense (as in 茶经 'tea classic'). Idiomatically, X经 means 'the accumulated wisdom on X', often said half-jokingly about a person's personal expertise. Compare 生意经 (business know-how).
culture
The oldest known work is 范蠡's 《养鱼经》 from the Spring and Autumn period — China's first aquaculture manual.
