一郎
Ichirô is actually
Japanese for "
first son" ("
ichi" is Japanese for
one).
In the olden days, before Japanese commoners had two names of their own, they would name their first sons Ichiro. Their next male children would be named 次郎 Jiro ("next son"), 三郎 Saburo ("third son"), 四郎 Shiro ("fourth son"), and 五郎 Goro ("fifth son").
While the kanji at the top of this writeup are, by far, the most common way to write the name, there are actually 28 different ways to write "Ichiro," each with a slightly different meaning.