The following description was prepared by William Gross:
The finials evolved from knobs at the upper end of the staves (Atzei Chaim) on which the Torah scroll is wound. Since the shape of the spherical finial recalled that of a fruit, it was called a tappu'aḥ, "apple," among the Jews of Spain and in the Sephardi Diaspora, and a rimmon, "pomegranate," in all other communities.
The earliest known reference to Torah finials occurs in a document from 1159, found in the Cairo Genizah, from which we learn that by the 12th century finials were already being made of silver and had bells. Around the same time, Maimonides mentions finials in the Mishneh Torah (Hilkhot Sefer Torah 10:4). Despite the variations on the spherical shape which developed over the centuries and the addition of small bells around the main body of the finial, the spherical, fruit-like form was the basic model for the design of finials in Oriental and European communities.
A most significant variation appeared in 15th-century Spain, Italy, and Germany, where the shape of finials was influenced by that of various objects of church ritual, whose design often incorporated architectural motifs, The resulting tower-like structure, which seems to have appeared around the same time in different parts of Europe, became the main type of finial in 18th-century Germany and Italy, as well as Morocco, brought there by Jews expelled from Spain.
Rimmonim from Galicia in Ukraine are relatively rare, but can often be identified by the very wide bases of the object. This might well reflect that at one time the Rimmonim were attached by nails or screws to the round plates above the rolled Torah Scroll staves, the Atzei Chaim. In Galicia, Rimmonim were called Atzei Chaim, perhaps because they were once attached to the wood and an integral part of the structure. The winding vegetal motif ascending the columns supporting the crown may well recall the columns of the Temple that are so often illustrated in Jewish texts in this vine-covered way.