I've always seen the acronym as HCI (Human-Computer Interaction) until recently when I've seen it as CHI on some news.yc posts (mostly microsoft-related, if I r

I've always seen the acronym as HCI (Human-Computer Interaction) until recently when I've seen it as CHI on some news.yc posts (mostly microsoft-related, if I recall...). Is there a significance behind this change that I'm missing?