”ай жерденсіз

”ай жер (what place) + the ablative case suffix + сіз: 'Where are you from?'

The ablative case suffixes:
After vowels and з, ж, л, й, р +дaн/+ден;
After м, н , ’ and the 3rd person possessive suffix +нaн/+нен
After voiceless consonants and б, в, г, д +тан/+тен

One use of the ablative case is to express the idea of 'coming from' (from where, from what, from whom). Case suffixes are placed before personal endings:
“ай жер+ден Where from?
“ай жер+ден+сіз Where are you from?
Америка+дан From America.
Америка+дан+мын I am from America

Note the difference between:
“ай жерде? [Locative case: where (аt)?] Америкада 'in America.'
and
“ай жерден? [Ablative case: where from?] Америкадан 'from America.'