kosalla : [nt.] proficiency; cleverness.

A.P. Buddhadatta Mahathera, Concise Pali-English and English-Pali Dictionary [available as digital version from Metta Net, Sri Lanka]

Kosalla (nt.) [der. fr. kusala] proficiency. There are 3 kinds mentioned at D iii.220, Vbh 325 & Vism 439 sq., viz. āya˚, apāya˚ and upāya˚; at Dhs 16=20=292= 555=Nd2 ad paññā it is classed between paṇḍicca and nepuñña. See also Pug 25; Vism 128 sq. (appanā˚), 241 sq. (uggaha˚ & manasikāra˚), 248 (bojjhanga˚); PvA 63, 99 (upāya˚).

Pali-English Dictionary, TW Rhys Davids, William Stede,