Might and main

[…] I found myself hanging on the skysail-yard, holding on might and main to the mast; and curling my feet round the rigging, as if they were another pair of hands.

c.1890s, Giovanni Boccaccio, James McMullen Rigg (translator), The Decameron, Novel 1, 6, […] he strove might and main to pass himself off as a holy man […]

When the sunlight threads the pine-gloom he is fighting might and main / To clinch the rivets of an Empire down.

with might and main

Mr. Winkle, catching sight of a lady's face at the window of the sedan, turned hastily round, plied the knocker with all his might and main, and called frantically upon the chairman to take the chair away again.

Thinking that we were about to be taken up under the act for the suppression of vagrancy, we flew out of the house, sprang into a canoe before the door, and paddled with might and main over to the opposite side of the lake.

The good mothers, like Burns’s matron, are plying their needles, making "auld claes look amaist as weel’s the new;" while the domestics, or help (we prefer the national descriptive term), are wielding, with might and main, their brooms and mops, to make all tidy for the Sabbath.

"I feel just like studying with might and main," she declared as she brought her books down from the attic.

Another horrific attack on tourists to Dublin in the city centre and in the height of summer. Gardaí are doing their job with might and main.