From The Chemistry Book

Discovered by Ernest Rutherford between 1911 and 1919, protons are positively charged subatomic particles located in the nuclei of an atom. The proton is a baryon and is considered to be composed of two up quarks and one down quark.

The term proton itself was coined by Rutherford; the word proton is derived from the Greek 'protos,' meaning 'first.'^[1] The term first appears in print in 1920. ^[2]

References

1. ↑ Cover of Ernest Rutherford's landmark 1919 paper
2. ↑ Dr. Lee Sawyer, Assist. Professor of Physics, Louisiana Tech Univ.