Term heterosis was introduced by

Term heterosis was introduced by Shull (1914).
Heterosis, hybrid vigour, or outbreeding enhancement is the improved or increased function of any biological quality in a hybrid offspring. An offspring is heterotic if its traits are enhanced as a result of mixing the genetic contributions of its parents.
In proposing the term heterosis to replace the older term heterozygosis, G. H. Shull aimed to avoid limiting the term to the effects that can be explained by heterozygosity in Mendelian inheritance.