Phalanx: Anatomically, any one of the bones in the fingers or toes. (Plural: phalanges.) There are 3 phalanges (the proximal, middle, and distal phalanx) in most of the fingers and toes. However, the thumb and large toe have only two phalanges that accounts for their being shorter.
A "phalanx" in ancient Greece was a military formation composed of heavily armed troops in close deep ranks. The soldiers stood shoulder to shoulder, several rows deep, often with their shields joined. A phalanx was a formidable group that was difficult to penetrate.
The bones in the fingers and toes were first called "phalanges" by the Greek philosopher-scientist Aristotle (384-322 BC) because they are arranged in ranks suggesting the military formation.