Ya°: 2. Use of nt. forms. © as adv. deictive “so,” in combn with var.
It’s discussed on Wikipedia. But basically it refers to a term who’s meaning must be derived from context. In Pali, as in this case, it frequently refers to such terms as ca or vā, where the terms are repeated after each item in a list. The coordination of relative (ya) and demonstrative (ta) pronouns is another case.
Thanks for the detailed answer Bhante Sujato. 
Might you have been thinking of “deictic”?
Deictic pronouns are hallmarks of the oral tradition when the speakers could use their hands to gesture to things designated by their pronoun. Eg, ida.m means “this” but when it is used in a same sentence with aya.m (this), it takes on the meaning “that” to refer to something other than this/aya.m.
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