In the paper "Lexical Inventions: French Interlanguage as L2 versus L3" (Applied Linguistics, 19.4 (1998)), Jean-Marc Dewaele refers to a paper by E. Haugen ("The Analysis of Linguistic Borrowing", Language, 1950), who proposed a taxonomy of crosslinguistic borrowings (emphasis added):
He distinguished loanwords (without morphemic substitution), loanblends (with partial morphemic substitution) and loanshifts (with total morphemic substitution). He observed that some loanblends were in fact 'hybrid creations' (1950 221), not part of the borrowing process but presenting evidence 'of an intimate fusion into the language of the borrowed material, since it has become productive in the new language' (ibid ).
Haugen mentioned "bordo" (boarder) as an example of a loanblend by a Puerto Rican learner of English. (The term loanblend is also in Wiktionary, where it is defined as "A compound word or expression consisting of both native and foreign elements.")
"Hypothecation" looks like the Spanish word "hipoteca" that has become productive in English, i.e. by adding the common suffix "-ation".
Loanblends are a specific example of the more general phenomenon known as lexical transfer, which also includes false friends, and calques or literal translations from the L1. (See also An Overview of Variables Affecting Lexical Transfer in Writing: A Review Study by María Pilar Agustín Llach, International Journal of Linguistics, 2010).