As society evolves, so too does language. In a changing society, you will want to be careful with word choices so as not to offend someone, but when doing research you may have to use historically relevant terms to find pertinent research. Many words and terms considered acceptable in previous decades and centuries are now recognized as demeaning, exclusionary, and derogatory. These terms are known as “pejorative” words. Thorough research can often be more successful when these pejorative terms are used to search historical and literary sources, even if it is uncomfortable to do so.
Also noteworthy are the ways in which people who are members of different ethnic, social, cultural, or racial refer to themselves have changed over time. For example, Queer was once a negative adjective to describe a person of same-sex orientation but is now a chosen moniker for some. Latin American, Chicano, Latino/a/x, Spanish-American, and Hispanic are all various names for people with a heritage tracing back to Spain or Hispaniola. African-American is a term that only gained acceptance in the 1990s, Terms such as Black, Negro, Colored, People of Color, and Afro-American are all terms used historically.
Please note that the subject headings might use antiquated terms that need to be updated by the Library of Congress. There are thousands of subject headings and cultural changes to language that occur frequently, so these terms may or may not reflect popular terminology.