Definition of top up

The expression "top up" originated in the mid-20th century, particularly through the colloquial and informal usage of the British television industry. In this context, "top up" referred to the act of adding additional programming to a television schedule in order to fill in any gaps or interruptions, particularly during live broadcasts. The phrase's usage was later adopted by the British telecommunications industry to describe the process of adding value or credit to a pre-paid mobile phone, which is sometimes referred to as a "top-up." This usage has since spread to other countries, including the United States and Australia, where it is now commonly used to refer to the act of adding money or value to a variety of prepaid services, such as electricity, transportation, or water meters. The literal meaning of "top up" is to add a further or additional amount to a supply or container that has already reached its capacity, ultimately resulting in a replenishment of the item or service in question. The metaphorical use of the term in contemporary English encapsulates the notion of enhancing an existing resource by adding more, whether it be money, time, or some other valuable commodity.