From this sūtra up the the aphorism kaḍārāḥ karmadhāraye [[2.2.38]] only one name of each thing named is to be understood.,
What is that name then? That which comes last, where the claims are otherwise equal (I. 4. 2.) and that which were its claim disallowed, would have no other opportunity of conducing to any result, would be the recognised name. As a short vowel is called 'light' by (I. 4. 10.) and it is also called 'heavy' when it precedes a conjunct consonant 1.4.11. Thus a short vowel has two names 'light' and 'heavy.' But it will not be called 'light' when it precedes a conjunct consonant, but will have only one name, i.e. 'heavy.' Thus in भिद to divide छिद to split, the इ is 'light' while the same letter is 'heavy' in शिक्षा teaching भिक्षा begging.
Thus in the root तक्ष् the अ is 'heavy' and therefore in forming its aorist we have the form अततक्षत्. Similarly अररक्षत्. The rule 7.4.93 not applying here as that rule is applicable to laghu vowels only.,