In American Sign Language, individuals fingerspell the names of individuals and other proper nouns, words that do not have signs, technical words and acronyms. It is acceptable to fingerspell a person's name, and individuals typically do so during initial introductions. However, a member of the deaf community may have a special sign for his name or a name sign.
People using sign language fingerspell names of places and things, such as London or Jupiter, provided no acceptable ASL sign exists. This is the case with flowers; there is only a sign for rose, as of 2015. People use fingerspelling for all other names of flowers. Also, if a signer does not know the existing sign for a place or thing, the signer may fingerspell it as well.
With ASL, people fingerspell any words used for emphasis and popular brands. It is helpful to fingerspell a sign when clarifying its meaning, since many individual signs translate into multiple English words. For example, with slight variations by speaker, the ASL word for potato also indicates Ireland and even Idaho, depending on context.
ASL signers usually fingerspell borrowed words. Over time, this fingerspelling mutates into lexicalized fingerspelling, or fingerspelling that looks like a sign. The same rules apply as for all fingerspelling, except that the list of lexicalized words is somewhat specific and includes the words such as "busy," "what," "job" and "if."