1 leave, go away, with implication of hurrying: Is that the time? I’ve goat tae nash! 19-.
2 to acompany: When we walk oot they're aa impressed. He only nashes wi the best. 20-.
noun, also nasher a deserter 19. etymology: from Romany naš- ‘to flee’ from Sanskrit naś- ‘to be lost, perish, disappear, run away’; attested by Galloway Tinkler-Gypsies, BS in TDITA; also collected by EMcC/PS; nasher also collected by Simson (1865) note:

Grose and Egan (1823) define as ‘To go away from, or quit, any place or company…’. The verb has passed into use in Edinburgh and the surrounding areas. It appears to be used especially by schoolchildren who then, in adulthood, seem to discard it.

OED describes it as ‘Cant obsolete’.

Grellmann (1787) collected the forms Naʃch ‘to flow’ and Nazh ‘to hunt’ from Continental gipsies.

Canadian Paul Pope (2013) cites this and he defines it as ‘to go away’.