Oh! PMSL!

Well, I've got nothing against penis's but my reasoning for the name is below:

Bija is a Sanskrit term - commonly used in both Buddhism and Hinduism - and means origin, root, or seed. One of its most common uses is referring to a 'seed' syllable, sound, or mantra.

The symbol used on the bija logo below is for the seed syllable 'hum'. This mantra may be used by a yogi or vedantin wanting to work with their ability to communicate as it is associated with speech (so they may meditate on it or chant the sound for example).

So you could see it as a mantra for 'freedom of speech'.