Floruit , abbreviated fl. (or occasionally flor.), Latin for "they flourished", denotes a date or period during which a person was known to have been alive or active. In English, the unabbreviated word may also be used as a noun indicating the time when someone flourished.
Broadly, the term is employed in reference to the peak of activity for a person, movement, or such. More specifically, it often is used in genealogy and historical writing when a person's birth or death dates are unknown, but some other evidence exists that indicates when he or she was alive. For example, if there are wills attested by John Jones in 1204, and 1229, and a record of his marriage in 1197, a record concerning him might be written as "John Jones (fl. 1197-1229)".
In some cases, it can be replaced by the words "active between [date] and [date]", depending on context and if space or style permits.
fata morgana Morgan.