UNCLE, a. colloquially, rustic and rude person.
If it is not an error per uncle, it must be a lexical component usually used in chemistry to name sulfur, which comes from Greek 952; 949; 953; 959; 957; (theíon ) with the same meaning.
In Chemistry is a prefix that is used to indicate that the substance contains Sulfur . My father's brother or my mother's brother.
UNCLE: prefix that means, " sulphur ".