Karate: 唐 vs 空.

This article on Slate says that karate (空手) as a Chinese form was tweaked in the 1920s for marketing in Japan, and that the process involved changing the kanji kara, "sky/empty". From what?

Wikipedia says that karate's kara was originally 唐 (kara/TOU)*, which Saiga tells us means the Tang dynasty. (Apparently it also means "nonsense/futile"—reminiscent of 漢, which means Han China but also can mean man-with-negative-connotations, as in 痴漢 chikan, a molester/groper, and 暴漢 boukan, a thug.) The Slate article says rather glibly that [w]ith a few deft scribbles, the character for kara was adjusted to emphasize its meaning as "open."—but the change seems neither a question of emphasis nor a few deft scribbles.

Changing to 空 does make sense, though, if part of the aim was to get away from Okinawan martial use of farm implements. Hmm.

Update: A sec ago I was looking for calligraphy examples of 唐 and 空, to emphasize that we're not talking about a few deft scribbes...and when I entered kara the Microsoft IME offered me 漢. Interesting!

*Seems the second kanji in "Tang dynasty" is 朝—asa/CHOU, morning. What's up with that?