Pronunciation: [dˈuː tˈɒp ɒv hˈɛd] (IPA) 
The phrase "do top of head" is commonly misspelled as "off the top of my head." The correct spelling uses the word "do" instead of "off" and is derived from the slang phrase "do something on the top of one's head" meaning to improvise or think on one's feet. The correct pronunciation of "do top of head" is [duː tɒp ɒv hɛd] with emphasis on the first syllable of "top" and a British English pronunciation of "head."
The phrase "do top of head" is an idiomatic expression that is commonly used in informal conversations. It is typically used when someone is asked a question, and they respond without giving it much thought or consciously considering the answer. In this context, "do" refers to the act of providing an answer or response, while "top of head" refers to the spontaneous nature of the response.
This phrase implies that the answer being given is not based on deep thought or factual knowledge, but rather on the individual's immediate instinct or guess. It suggests that the person is providing an answer solely based on what quickly comes to mind, without using any specific information or considering the accuracy of their response.
For example, if someone asks another person, "What is the capital of Australia?" and the person responds with "Sydney," they may add the disclaimer "I'm just doing top of head" to indicate that their answer may not be well-considered or entirely accurate.
In essence, "do top of head" is a colloquial expression that signifies a spontaneous or unreflective response to a question. It highlights the lack of certainty or forethought in an answer and is often used to indicate that the information provided may not be reliable or entirely accurate.
