He is head in with his work

Some friends were discussing a friend’s recent concentration on work. This is a mashup of “head on” (directly, without hesitation) snd “all in” (fully committed to a task or endeavor). “Head down” (avoid attention or trouble) might also be in the mix. Perhaps the speaker was indicating his friend was not only focused on work but also in staying out of trouble? A big thanks to Ben Geier for uttering this one and Kevin Hatfield for hearing it and sending it in.