Buckle down
(PW) study or work very hard
Last semester his grades were very low, so this year he decided to buckle down.
(phraseFinder)
Meaning
Apply oneself to hard work.
Origin
This is a US phrase, although it may well be related to an earlier British phrase 'buckle to', which means much the same thing. That dates back to the early 18th century, for example, from John Arbuthnot's story John Bull in The Law is a bottomless pit, 1712:
"'Squire South buckled too, to assist his friend Nic."
'Buckle down' is first cited in the American literary/cultural magazine Atlantic Monthly, 1865:
"If he would only buckle down to serious study."
(free)
buckle down vb
(intr, adverb) Informal to apply oneself with determination to buckle down to a job
(urban)
A slogan meant to convey 'Get to work!' or to say 'Quit lollygagging and get back to work!.
For example: Last week the section Boss walked through the office and caught one person surfing the net at their workstation instead of working and he therefore jumped to the conclusion that all the office workers must be doing it all the time. Ergo he gave a threat to the team boss's and then doled out the "Buckle down!" speech, which in turn was reiterated upon the employees.
(yours)
Set to work, apply oneself with determination, as in All right, we'll buckle down now and study for exams. Originating about 1700 as buckle to, the expression gained currency with the football song “Buckle-Down, Winsocki” (from the Broadway musical comedy Best Foot Forward, 1941). [Mid-1800s]