tavlin

The Hebrew word for "spice" is tavlin תבלין, with the plural tavlinim תבלינים. This usage goes back to Talmudic times (e.g. Shabbat 119a, Nedarim 51a). However, this appears to be the result of a mistake, for originally the singular form for spice was tevel תבל, and the Aramaic form tavlin was the plural (In the Ben Yehuda dictionary, Tur-Sinai writes that the original reading was like the Sefardi tevalin, but the Ashkenazim read the word as tavlin.) This is clear from such sources as Beitza 14a, where tavlin is used as a plural: תבלין נדוכין.

Klein provides the following etymology:

Related to תבלא ( = spice, seasoning), Arabic tabil ( = coriander; spice, condiment, seasoning), tabbala, taubala (he spiced, seasoned). These nouns probably denoted originally a certain plant (compare Syriac תבלא - 'tordylium, hartwort, meadow saxifrage'), whence, with sense enlargement, 'any plant used for seasoning', whence 'spice' in general.

The Arabic word is the source of the salad tabbouleh (or tabouli) - meaning "little spicy".

Joseph Lowin, however, suggests a different origin here:

probably derives from an older, primary root, ב-ל-ל (bet, lamed, lamed), meaning "to mix." When you add spices to food you are creating a savory mixture; alternatively, many spices added to foods are in fact mixtures of different spices.

Both agree that the word tevel תבל, meaning "world" is not related.

We also find the verb form to spice - תבל. Ruth Almagor-Ramon writes that although tavlin overcame tevel as the singular noun for "spice" (after serious debate among linguists in the last century - see Yad Halashon p. 608), there's no reason to adopt תבלן as the verb. Similarly, metubal מתובל and not metublan מתובלן should be used for "spiced".

Mistaking a plural for a singular is perhaps more common in Modern Hebrew, where many words are borrowed from English, which uses "s" to indicate a plural. However, in Hebrew, the sound "s" has no such significance, so the plural of "jeans" becomes "jeansim", "brakes" becomes "brakesim" and "chips" becomes "chipsim". Another example is the word burekas בורקאס, the popular puff pastry. Modern Hebrew borrowed it from the Turkish börek (perhaps via Ladino), and again made the plural form a singular one - so the plural in Hebrew is now bourekasim. This leads English speaking immigrants to refer to one pastry as a bureka - which certainly doesn't work in Hebrew. There might even be some Hebrew linguists who would prefer this form, but as Stahl writes, it's not terribly relevant - for who can eat only one?