The term interfix has been used for two kinds of phenomena: (i) meaningless elements that occur inside compounds as "linkers" of the two stems (e.g. German Liebe-s-brief 'love letter'), and (ii) meaningless elements that occur between the stem and a derivational suffix (e.g. Spanish camion-c-ito 'little truck').
The term interfix goes back to the 19th century (e.g. Haldeman 1865). In spreading the use of interfix for Romance pre-suffx elements, Malkiel (1959) has been influential.
- "Affixes are additions to roots, stems, and words, serving to modify their meaning and use. They are of two kinds, prefixes, those at the beginning, and suffixes, those at the end of the word-bases to which they are affixed. Several affixes occur in long words like in-com-pre-hen-s-ib-il-it-y which has three prefixes and five suffixes. The term interfix is hardly necessary for ad in anim-ad-vert, or t inserted as a fulcrum between two vowels as ego-t-ism." (Haldeman 1865:§65, cited from OED)
- Haldeman, Samuel S. 1865. Affixes in their origin and application, exhibiting the etymologic structure of English words.
- Malkiel, Yakov. 1958. "Los interfijos hispánicos." In: Catalán, D. (ed.) Estructuralismo e historia II: Miscelánea Homenaje a André Martinet. Tenerife: Universidad de La Laguna, 107-187.