Trade Tongue is the lingua franca of the Trade Culture and its associated regions. It is spoken by many individuals who deal with more than one culture, and especially by those whose business takes them across species lines.
Trade Tongue's origin is in such interspecies dealings; it began as a merchants' jargon among early traders between dwarven and human communities circa -450 to -250 GR (1000-1200 years before present). The core of the language was derived from Gêchkatalo, the language of the dominant dwarven state of the time. The language has evolved away from its precursor considerably over the last thousand years.
The words for basic numbers have changed only slowly, but the numeric system has been greatly expanded and regularized.
Trade Tongue has numerous dialects over the area in which it is spoke but, true to its original purpose, they tend to remain mutually intelligible. The most significant differences in the dialects are vocabulary, due to Trade Tongue's maintenance of an active tradition of borrowing words from the languages around it.
Most speakers of Trade Tongue do not speak it as a native language, except in some particularly cosmopolitan areas (most notably Tâl Katar), where many do speak Trade Tongue natively. The other major except is that a large majority of gnomes have more or less abandoned older, natively gnomish languages in favor of speaking Trade Tongue as a first language. This naturalization among the gnomes has lead to what is probably the most distinctive of the Trade Tongue dialects.