inestimable (adj.) Look up inestimable at Dictionary.com
late 14c., "beyond estimation," from Old French inestimable (14c.) or directly from Latin inaestimabilis, from in- "not, opposite of" (see in- (1)) + aestimabilis (see estimable). Meaning "too precious to set a value on, priceless" is attested by 1570s. Related: Inestimably.