Dear Margaret,
Taam "taste" is highly unlikely, even as an allusion, for phonological and morphological reasons - the word is /ta:m/ or /tam/ in, I think, all dialects from the Atlantic to the Ural, including those who have a wider a -> o shift ("shobbesdike" or "tote-mome" loshn), and I can think of no convincing explanation for the -or, including a phonetic or spelling variant of Germanic -er.
Secondly, however common dates may have been on the German-Jewish Pesach table, the imagery of dates was strong through the ages, and particularly so exactly in the period in question, when Palestine was more concretely in people's minds among Zionists and non-Zionists, and as part of the general German and European culture of "Orientalism". The association was probably simply that, and nothing concrete, such as eating dates or using palm oil in the product.
But brand names are tricky in that they can indeed come about from a forced twist. Off the cuff, why not "Pesach - to mor!" coined by somebody in a Slavic environment, meaning "Passover - that's marge!" I'd be very surprised, but any such origin is possible in theory. Or maybe the daughter of the owner was called Tamara or right ahead Tomor. Early for the latter, but not excluded. Or they were a couple with the first names of Pesach and Tomor, etc. etc....
Best wishes,
Phillip Minden