Loath, a.
Etymology: [OE. looth, loth, AS. la hostile, odious; akin to OS. l, G. leid, Icel. lei, Sw. led, G. leiden to suffer, OHG. lidan to suffer, go, cf. AS. li to go, Goth. leipan, and E. lead to guide.]
1. Hateful; odious; disliked. [Obs.] Chaucer.
2. Filled with disgust or aversion; averse; unwilling; reluctant; as, loath to part. Full loth were him to curse for his tithes. Chaucer . Why, then, though loath, yet must I be content. Shak.
Shades of meaning
Fernald has no entry of its own for loath; he lists it under reluctant.
Where he writes about it:
Reluctant (L. re, back, and lucto, strive, struggle) signifies struggling against what one is urged or impelled to do, or is actually doing; averse (L. a, from, and verto, turn) signifies turned away as with dislike or repugnance; loath (AS. lath, evil, hateful) signifies having a repugnance, disgust, or loathing for, tho the adjective loath is not so strong as the verb loathe. — from reluctant
A man is loath to believe evil of his friend, reluctant to speak of it, absolutely unwilling to use it to his injury. — from reluctant