The almond is native to the Middle East and Asia, but the largest almond producer in the 21st century is the United States with nearly two thirds of the world’s crop produced there. The almond is more closely related to peaches than other nuts; the nut we eat being part of the pit of the almond fruit.
There’s two kinds of almonds which have been historically used in gin. The first is the aforementioned sweet almond which you can purchase in stores and snack upon. The second kind of almond is the bitter almond, which is so called because of its relatively high proportion of cyanide. In small amounts they were traditionally used to flavor amaretto. This kind has been largely replaced by apricot kernels in the modern day, though traditionally it’s likely that bitter almonds may have been the almond of choice.
Today your gin, if it contains almonds, is using the sweet almond which due to a genetic mutation contains none of the toxin of its ancestors. The flavor of almond in gin, albeit subtle, calls to mind the creamy, slightly vanilla tinged exotic flavor of almond syrup and orgeat.