Cognate: A cognate of a word is a word in another language which is derived from the same root.

• Example (1): the English word mother has cognates in several other Indo-European languages: Greek μητηρ (meter), Russian мать (mat'), German mutter, Sanskrit matri, and Irish mathair. These words all share a similar sound, and thousands of years ago they were all the same word in the same language.
• Example (2): Cognate given names also exist. Andrew, André, Andrea, Andrey, Andrzej and Ondrej are all cognates derived from the Greek root name Ανδρεας (Andreas).

Diminutives: A diminutive (or pet name) of a given name is a short and/or affectionate form. Often they are only used by friends and relatives.

• Short forms: The most common diminutives (at least among English names) are those that are short forms of the original name, very often from the first syllable or sound of the name. For example, Alex is from Alexander, Barb is from Barbara, Deb is from Deborah, and Mike is from Michael. Other short forms don't come from the beginning of the name, but instead from the end or the middle, like Beth from Elizabeth, Fred from Alfred, Greta from Margareta, and Lisa from Elisabeth.
• Suffixes: Diminutives can also be formed by adding a suffix to the original name or the name's short form. In English, the -y/-ie suffix is very common, leading to diminutives like Abby, Debbie, Charlie, Johnny and Sammy.
  • Italian diminutives: use the -ino/-ina suffix (ultimately from the Latin masculine -inus or feminine -ina meaning "belonging to"). It can be seen in the names Giorgino, Giuseppina and Luigino. The -etto/-etta diminutive suffix gives rise to Antonietta, Giulietta and Simonetta.
  • French feminine diminutives: often use -ette, as in Annette and Jeannette. The -ette and -ine suffixes can also make masculine names feminine, as in Antoinette from Antoine, Georgine from Georges, Henriette from Henri, and Paulette from Paul. The French also use -on (Alison, Manon and Ninon) and -ot/-otte (Charlot, Charlotte, Jeannot and Margot).
  • Russian diminutives: are formed using many different suffixes. These include -sha (Masha for Mariya, Misha for Mikhail, Natasha for Nataliya, and Sasha for Aleksandr or Aleksandra) and -ya (Anya for Anna, Kolya for Nikolai, Petya for Pyotr, and Zhenya for Yevgeniya), as well as -ik, -nka and -shka.
  • Others include:
    • -ito/-ita in Spanish - Anita, Carlito, Juanita and Pepito.
    • -je/-tje in Dutch - Antje, Liesje and Maartje.
    • -an/-in in Irish - Aidan, Kevin, Máirín and Ryan.
    • -ag in Scottish - Beileag, Morag and Seonag.
    • -ek in Polish and Czech - Bolek, Jarek, Jurek and Radek.
    • -ska in Hungarian - Annuska, Juliska and Mariska.
    • -ka/-ko in various Eastern European languages - Branka, Ivanka, Stanko and Zlatko.
• Others:
  • Sometimes sounds that were difficult to pronounce (especially by children) were omitted or altered, resulting in diminutives. The difficult Norman r sound in medieval English names was often dropped (as in Babs for Barbara, Biddy for Bridget, and Fanny for Francis) or changed (as in Hal for Harry, Molly for Mary, and Sally or Sadie for Sarah). Likewise, the th sound was often changed, as in Dot for Dorothy and Betty or Bess for Elizabeth.
  • Rhyming nicknames were also used. Robert might be known as Rob, Hob, Dob or Nob (although Hob, Dob and Nob have since died out, they are preserved in surnames such as Hobson, Dobb and Nobbs). Likewise Roger might be Rodge, Hodge, Nodge or Dodge and Richard might be Rick, Dick or Hick.
  • The diminutive Ned for Edward resulted from the medieval affectionate phrase mine Ed(ward), which was later reinterpreted as my Ned. Other examples of this formation include Nan (later Nancy) for Ann, Nell for Ellen, and Noll for Oliver.
  • Diminutives such as Bill for William, Bob for Robert, Peg for Margaret, Polly for Molly/Mary, and Ted for Edward are not readily explainable.
  • Some Spanish diminutives also bear little resemblance to the originals, such as Chucho for Jesús and Charo for Rosario.