About the fingers: the name for the thumb is really old and possibly derived from an Uralian root word meaning "edge" or "rim", aka it's the finger on the edge or rim of the hand. According to
Kielikello, a publication concentrating on Finnish language, "peukalo" is mentioned for the first time In Finnish literature (which didn't exist before the 16th century) in 1540s, "keskisormi" in 1644, "etusormi" in 1738, "nimetön" in 1745 and "pikkusormi" in the 19th century. Before this pikkusormi was known as "sakarisormi" , "peg finger", mentioned in literature already in the 16th century.
In addition to the official names fingers have lots of different names in dialects, often derived from their uses. The index finger, etusormi, especially has many: nuolusormi = "licking finger", nenäsormi = "nose finger", potinnuolija = "pot licker", tupakkanäppi = "tobacco finger" and voinlappaja = "butter scooper".
Keskisormi is also called isosormi = "big finger" or koukkusormi = "hook finger", the last one because it's the finger used in the traditional game
sormikoukku, "finger hook".
Nimetön is just nimetön, "nameless", because it was believed to have magical powers which had to be protected by not naming the finger.
Pikkusormi has mostly different versions of names meaning "little" but has also been called piippasormi, "sprout finger".
Peukalo tends to be peukalo everywhere but gets funny additions like peukalopukki, "thumb billygoat", in children's rhymes - in which all fingers tend to have a myriad of funny nonsense names.
