Phil,

Could be because he was Ham's kid. Noah's grandson. Ham was the one who 
peaked at Noah while he was naked and drunk and then told his brothers who 
then went in walking backwards to cover Noah's indecency up. Noah found out 
what happened and God cursed Ham and his descendents... see below the 
Nimrod reference here...

 From Nelson's Bible Dictionary:

NIMROD
NIMROD
[NIM rahd] (meaning unknown)-a son of Cush and grandson of Ham, the 
youngest son of Noah (Gen 10:8-12; 1 Chron 1:10). Nimrod was a "mighty one 
on the earth"-a skilled hunterwarrior who became a powerful king. He is the 
first mighty hero mentioned in the Bible.
The principal cities of Nimrod's Mesopotamian kingdom were "Babel, Babylon, 
Erech, Accad, and Calneh, in the land of Shinar" (Gen 10:10). From the land 
of Babylon he went to Assyria, where he built Nineveh and other cities (Gen 
10:11). In Mic 5:6 Assyria is called "the land of Nimrod."
The origin and meaning of the name Nimrod is uncertain, but it is doubtful 
that it is Hebrew. It is probably Mesopotamian, originating from the 
Akkadian (northern Babylonian) god of war and hunting, Ninurta, who was 
called "the Arrow, the mighty hero."

HAM
HAM
[hamm] (hot)-the name of a person and two places in the Old Testament:
1. The youngest of Noah's three sons (Gen 5:32). Ham, along with the rest 
of Noah's household, was saved from the great Flood by entering the ark 
(Gen 7:7). After the waters went down and Noah's household left the ark, 
Ham found his father, naked and drunk, asleep in his tent. Ham told his 
brothers, Shem and Japheth, who covered their father without looking on his 
nakedness. Noah was furious because Ham had seen him naked, and he placed a 
curse on Ham and his descendants. The offspring of Ham were to serve the 
descendants of Shem and Japheth (Gen 9:21-27).
Ham had four sons: Cush, Mizraim, Put and Canaan (Gen 10:6). The 
descendants of these four are generally thought of as immoral and evil. The 
tribe of Mizraim settled in Egypt, while the tribes of Cush and Put settled 
in other parts of Africa. The tribe of Canaan populated Phoenicia and 
Palestine.
2. A city east of the Jordan River during the time of Abraham. It was 
attacked by Chedorlaomer and other allied kings (Gen 14:5). The modern city 
of Ham lies six kilometers (four miles) south of Irbid.
(from Nelson's Illustrated Bible Dictionary, Copyright (c)1986, Thomas 
Nelson Publishers)