on one's own account
Also, on one's own hook or initiative. For oneself; also, by one's own efforts, as in I've gone into business on my own account, or He called the police on his own hook, or She went job-hunting on her own initiative. The first term, first recorded in 1801, transfers the financial sense of account to one's own interest or risk. The hook variant, a colloquialism, was first recorded in 1812 and the precise analogy is unclear. The second variant, using initiative in the sense of “enterprise,” was first recorded in 1858.