Mendeleev’s prefixes eka, dvi, and tri came from Sanskrit.
He used these words as temporary labels for predicted elements that occupied positions below known elements in the same group. Eka means “one,” dvi means “two,” and tri means “three,” indicating that a missing element lay one, two, or three places down from a familiar reference element.
The system became famous through predictions such as eka-aluminium, eka-boron, and eka-silicon. These placeholders corresponded respectively to gallium, scandium, and germanium, discovered in 1875, 1879, and 1886. Mendeleev’s terminology was descriptive rather than a claim that the eventual elements would permanently retain those names.
The Sanskrit connection may also reflect Mendeleev’s relationship with Sanskritist Otto von Böhtlingk and his interest in Pāṇini’s highly systematic grammar. A common mistake is to call the prefixes Greek or Latin because scientific naming often uses those languages; these particular numerical prefixes were Sanskrit-derived.