The adverb "tightly" refers to something being secured or held firmly in a close manner. It can describe physical objects being held together without any looseness or can be used more abstractly to express strict adherence to rules or concepts. When something is done "tightly," it is executed in a precise, controlled, or efficient manner.
The word "tightly" comes from Middle English "tiht," meaning "firm" or "strict," combined with the adverbial suffix "-ly." The root word relates to the Old English "tīht," which also implies firmness or strength.