Green’s Dictionary of Slang

mung v.²

(UK tramp/Und.) to beg.

1606		P. Holland (trans.) Suetonius’s Historie of Twelve Caesars (1899) I 137: He was none of these that lie in the winde to mung and catch at Inheritances.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1859		Matsell Vocabulum.
1865		Leaves from Diary of Celebrated Burglar 21/1: You have ‘munged’ (begged) six ‘deeners’ already.
1871–82		B.M. Carew Life and Adventures.
1893		P.H. Emerson Signor Lippo 52: Many’s the time you’ve been waiting on me coming home to give you some of the grub I’ve munged.

In derivatives

munging (n.)

begging.

1859, 1860		Hotten Dict. of Modern Sl. etc.
1864, 1867, 1870		Hotten Sl. Dict.