buckle to

From buckle + to.

buckle to (third-person singular simple present buckles to, present participle buckling to, simple past and past participle buckled to)

1. (intransitive, idiomatic, informal) Synonym of buckle down (“to apply oneself to study, or a task or work; to focus on or take a serious attitude towards something; to put forth the needed effort”)
   • 1929, D[onald] J[ohn] Munro, “Nemesis”, in The Roaring Forties and After, London: Sampson Low, Marston & Co., →OCLC, page 38:

     Then the sergeant let us out, and introducing us to a pile of wood and saws and axes, informed us that when this had been cut up into firewood we should get our breakfast. He sat at the door of his kitchen watching, and seeing there was nothing else for it we buckled to and soon had the job done; when we were admitted to the kitchen and given a really good meal.

• [John Camden Hotten] (1859) “BUCKLE TO”, in A Dictionary of Modern Slang, Cant, and Vulgar Words, […], London: John Camden Hotten, […], →OCLC.