What is the origin of the idiom "hang in there" and when to use it?

The idiom "hang in there" emerged in the mid-20th century and gained significant popularity during the 1970s through the widespread circulation of motivational posters featuring a determined kitten clinging to a branch. These posters became iconic symbols of resilience and perseverance as time went on. This expression is frequently used in personal conversations, as well as in professional settings such as work environments or academic settings, to uplift and motivate individuals during times of stress, uncertainty, or adversity.