"Stay in your bubble", "don't break your bubble" - these were all expressions New Zealanders got used to hearing throughout lockdown.
Now, we talk about transtasman bubbles and travel bubbles - and the concept has become part of our everyday vocabulary.
Prime Minister Jacinda Ardern adopted the concept in the early days of the coronavirus pandemic, as a way to easily explain to New Zealanders how they needed to stay isolated to help fight the virus.
Now, the man who came up with the concept of the bubble has spoken about his reaction to the uptake on his idea.
Dr Tristram Ingham, a senior research fellow in the Department of Medicine at the University of Otago in Wellington, came up with the concept while advising the Ministry of Health on the pandemic response for the disability sector.
An article in Otago University Bulletin Board online reveals Ingham has been "surprised and delighted" by the take up on his idea.
"I remember the first time I saw Prime Minister Jacinda Ardern say it. It was like 'wow, she said it', our concept got out there," he told the Otago Bulletin Board.
"And there was a great sense of pride from within the disability directorate that we had contributed to the whole picture," the medical adviser and academic added.
Ingham's work, alongisde that of his collaborators, including his wife Bernadette Jones, a research fellow in the Department of Medicine, and fellow academics Dr Meredith Perry and Dr Brigit Mirfin-Veitch have reportedly been commended by director general of health Dr Ashley Bloomfield in a letter to Otago University's Vice-Chancellor Professor Harlene Hayne.
Bloomfield said Ingham's concept of the "bubble" helped frame life more positively under alert levels 4 and 3.
The concept was originally created for those with disabilities but it spread far wider than Ingham could have imagined.
The academic is also the national executive chairman for the Muscular Dystrophy Association of New Zealand, and lives with muscular dystrophy himself. He came up with the concept before the Prime Minister announced the alert level system New Zealand would be adopting.
His focus was on protecting people with disabilities from the pandemic.
"We didn't want at-risk communities to be passive recipients of their fate," he said.
"The methods had to be around empowering individuals and whānau to have control over their own life and situations for self-preservation."
Concepts of self-isolation and social distancing were harder to explain to the public, but the idea of the bubble was easier to understand.
"Bubbles are a universally known concept, which could be made appealing to children or to people that didn't have a public health background. They could think of a bubble as a fragile yet beautiful structure that has to be nurtured and preserved," Ingham explained.
"And it introduced the concept of making sure you don't burst your bubble."
Thinking of people with low literacy and those with English as a second language, Ingham and his team also came up with a video to act as a "visual representation" of the concept.
Two days before lockdown, Jones and Ingham's colleague enlisted the help of one of the couple's daughters, Emma Draper, who is an actress, to help produce the video.
Build your Bubble was then adopted by the Ministry of Health.
Once Ardern told Kiwis that they needed to "stay in their bubbles", the concept took off.
"What I think is quite interesting and ironic is that it seems to be being picked up internationally and a whole bunch of other academics are starting writing about what it means, and the symbology of it. In some cases they are reading more into it than I even thought at the time," he said.
"We were just working as fast as we could and we locked on to a concept and ran with it."