Is there a connection between the word zera זרע - "seed" and the skin affliction tzaraat צרעת - (frequently, although perhaps inaccurately, translated as "leprosy")?
The noun zera derives from the root זרע. In the kal form (zara), it means "to sow" or "to scatter seeds". In the hifil form, hizria הזריע it takes on the meaning "to inseminate." The word z'roa זרוע - "arm", or metaphorically "strength, might" looks like it comes from the same root. However, based on the Arabic cognates, we can see that they are not related. Zera is cognate with Arabic zara'a, whereas z'roa is cognate with dhira in Arabic.
Klein writes that tzaraat comes from the root צרע - "to become leprous." He says that it is cognate with the Arabic sara'a - "he threw to the ground, threw down" and sar' - "epilepsy". He adds that the biblical word tzir'a צרעה - "wasp, hornet", may also be related to the root meaning "he threw to the ground." He doesn't explain how either tzaraat or tzir'a are related to throwing down, but the BDB elaborates and says that tzir'a may have an original sense of "wounding, prostrating". In the notes in Ben Yehuda's dictionary, a theory is suggested that tzaarat is so named because it cause the person to literally "fall" ill.
Since sowing seeds involves throwing them on the ground, I thought perhaps the two roots might be related. However, I could not find any reliable sources that could prove such a connection, so I won't make such a claim. Another thing I noticed is that a number of Hebrew roots beginning with the letters זר have an association with throwing. Most obvious would be זרק - "to throw", and זרה - "to scatter, winnow". Perhaps one could also include זרם and זרף - both meaning "to flow." Again, I didn't find any master theory connecting these roots.
What do I do with a theory like this? Throw it away, or scatter the seeds to future readers, hoping that someday I'll be able to reap what I sow?