Middle school (6th grade) Student asking the question?
What is the origin of the greater (>) than and less (<) than signs?
The place were I look for information about mathematical symbols is the Earliest Uses of Various Mathematical Symbols. If you follow the link on that page to Symbols of relation there is a note on less than and greater than. It says that they first appeared in a book by Thomas Harriot which was published in 1631. However Harriot died in 1621 and it seems that the symbols < and > were not in Harriot's notes but added when his notes were published.
Make sure you look at the Symbols of relation page. There is an interesting note that suggests a connection to the First Nations people of the Americas. Since the < and > symbols were not in Hariott's notes this First Nations connection is probably not true, but it is an interesting story anyway.Harley