The affixes ktvā , kta and ktvātu get the iṭ augment after the root añc when meaning 'to honour or do something to show honour'.,
As अञ्चित्वा जानु जुहोति, अञ्चिता अस्य गुरवः 3.2.188, 6.4.30, 2.3.67 By 7.2.56 अञ्चु would optionally have caused इट् to come before ktva, and hence by 7.2.15 never before the Nishtha. This sutra ordains invariable addition of this augment. Why do we say when meaning 'to honor'? Observe उदक्तमुदकं कूपात्, 'the water is raised from the well'.,