This type seems to be pre-Latin, perhaps Gallic. The short entry in Kluge, online reads:
"Tieger. Sm ‛curd' per. wobd. (15th century), mhd. ziger, spahd. ziger. A word of the Alpine dialects. Origin uncertain."
Hubschmied 1936, 93–95, suggested a Gallic etymon *tsigros or *tsigronos 'second warming'; the second form is necessary to explain the Romansh morpho-lexical type with a stressed suffix (Tschagrun). The dating given by Kluge is now outdated, as the word is already attested several times in the Consuetudines of the Hirsau monastery from the end of the 11th/beginning of the 12th century (cf. Bulitta 2018, 203). Hubschmied's approach is not weakened by this.
The restriction to West Upper German ("wobd.") claimed by Kluge must also be revised in view of the Tyrolean evidence on the VA map.

Seebold, Elmar (2012): Kluge. Etymologisches Wörterbuch der deutschen Sprache, Berlin, DeGruyter

Hubschmied, Johannes (1936): Ausdrücke der Milchwirtschaft gallischen Ursprungs: dt. "senn, ziger," lomb. "mascarpa, maoka, matü", Bern, in: Vox Romanica, vol. 1, Francke, 88-105

Link

Bulitta, Brigitte; Mikeleitis-Winter, Almut (2018): Vom Schweigen der Mönche Volkssprachige Bestandteile im Signa-loquendi-Kapitel der Consuetudines Hirsaugienses und das Althochdeutsche, Berlin, in: Sprachwandel im Deutschen. Herausgegeben von Luise Czajkowski, Sabrina Ulbrich-Bösch und Christina Waldvogel, De Gruyter, 181-212

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