1) The adjective was used of items that were of a good standard.
1519 Item that baxters make gude and able brede ... after the price off the corn, Selby, or simply intact, not requiring to be mended: c.1534 5 hable hogeshedes and 2 brokyn, Bridington. Used also of persons who were influential, possessed of material resources, status and wealth: 1642 The richest and ablest men in everie town ... should allwayes be subsidymen, Elmswell
1649 four of the ablest inhabitants of Old Byland. Note the following: 1533 he that kepes a wolkmynes [walkmilne] kepe a nayvill [an able] servand to serue men of towne, Wakefield
1628 hoping they will bring me honestlie to my burial according to my abilitie, Hartwith.
2) As a verb it was used of an apprentice or stranger being declared fit to practise his trade.
1410 To set uppe & occupy als maistre in the said crafte before he be searched & abled
1472 So put, abled, & admitted, York. More generally it referred to merchandise, judged to be of good quality: 1472 that they sell noy feche [fish] with owt it be abyld be fiche offesers, Selby.