When thinking about synonyms for the phrase "didst the top of head," several options come to mind. One possibility could be "off the top of one's head," meaning to speak without preparation or forethought. Another option might be "from memory," indicating that the information is recalled without the aid of notes or other resources. "Impromptu" or "unrehearsed" could also be used in a similar context. Alternatively, one could consider the phrase "on a whim," suggesting a decision made impulsively or with little consideration beforehand. Ultimately, there are countless ways to express the idea of speaking or acting without extensive planning, making this a versatile concept with many potential synonyms.