Native English speakers, why is such an "offensive" word used widely as a first name (details inside)?

Oh yeah! Successfully bypassed the mods and cheated the internet filters!

I mean the word “dick”.

If “dick” is offensive, why is it used as a first name? (Seriously, why did his parents called him “Dick Cheney”?)

As a non-native English speaker, I can’t understand it. Can you help me?