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It appears to be a regional, AmE usage:

Muckle:

To grab on to an object, usually with a great deal of force. May also be used figuratively to indicate a strong attraction for an object or person. Ex: "When I saw her down the bar, I muckled right on to her." Origin: Downeast Maine.

(Online slang dictionary)

Muckle

(US, dialectal) To latch onto something with the mouth.

  • 1954, Elizabeth Ogilvie, The Dawning of the Day‎1, page 199: And how'd she get such a holt on you, Terence Campion, let alone the way she's muckled onto those Bennetts?

(Wiktionary)