Origin of behalf
Word Origin for behalf
c.1300, behalve (with dative suffix), from Old English (him) be healfe "by (his) side," and on (his) healfe "on (his) side," from healfe "side" (see half).
in behalf of
Also, on behalf of.
For someone else, as someone's agent or representative. For example, In behalf of the board, I want to thank you for your help, or Joan was speaking on behalf of the entire staff. [c. 1300]
For someone's benefit or interest, as in He was collecting the dues in my behalf. [Late 1500s] Some authorities insist that in behalf of be used only to mean “for someone's benefit” and on behalf of only to mean “as someone's agent.” In practice, however, the terms are so often used interchangeably that this distinction no longer has a basis.
see in behalf of.