tatarabuelo

Etymology
Coined by analogy with tataranieto, and this of tratranieto, of the prefix tras- reduplicated and nieto; formerly trasabuelo was the usual term for our modern bisabuelo. Coromines dates the term around 1625

Noun

 * 1) great-great-grandfather great-great-grandmother for the feminine form
 * 2)  great-great-grandparent either a great-great-grandmother or a great-great-grandfather