In Tscheremissisches Wörterbuch known loanwords in Mari are usually noted as such, e.g. “taɣa ‘Widder, Hammel, Schafbock’ [< Tschuw.]”, “pülẟarem ‘fordern, verlangen’ [< Tat.]”. By going through the dictionary and compiling a list of unetymologized words, I’ve been able to propose a few new etymologies that hopefully will be published eventually. However, one must tread cautiously, as a few loanwords are left unmarked even when they have long been recognized as such.
One of these is the Mari word for ‘frog, toad’, listed under the headword užaβa with a great deal of dialectal variation. This bears a striking resemblance to Russian жаба id. Indeed, I turned to Savatkova’s Русские заимствования в марийском языке, and the loanword is included in the great big Russian–Mari index at the back (namely on page 95).
MariE taɣarl’a ‘ein kleiner Vogel’ is a borrowing of Tat. täkärlek, as recognized already by Räsänen in his Die tatarischen Lehnwörter im Tscheremissischen of 1923, p. 65. The word may have come into Mari through Chuvash mediation on account of the voiced velar spirant if one supposes that Mari did not take it from a Tatar dialect that voiced the velar, but that would still have merited writing “[< Tschuw./Tat.]” next to this headword like with other doubtful items, such as purlo ‘gräulich’.