Also see definition of "Footman" in Word Study
Study Dictionary
Footman
FOOTMAN [SMITH]
a word employed in the English Bible in two senses:- Generally, to distinguish those of the fighting men who went on foot from those who were on horseback or in chariots;
- In a more special sense, in (1 Samuel 22:17) only, and as the translation of a different term from the above --a body of swift runners in attendance on the king. This body appears to have been afterwards kept up, and to have been distinct from the body-guard --the six hundred and thirty-- who were originated by David. See (1 Kings 14:27,28; 2 Kings 11:4,6,11,13,19; 2 Chronicles 12:10,11) In each of these cases the word is the same as the above, and is rendered "guard," with "runners" in the margin in two instances - (1 Kings 14:27; 2 Kings 11:13)
Also see definition of "Footman" in Word Study