Why "motherboard" is used to refer to main board of computer
Solution 1:
It's called a motherboard because it is the main circuit board in the computer, and it can be extended by plugging other circuit boards into it. These extensions are called daughter boards. Wikipedia suggests that historically a "mainboard" was not extensible in this way, hence the need for different terminology. Many computer terms use human or biological words as metaphors:
- Master/Slave (controller and devices)
- Male/Female (plugs and ports)
- Mouse
- Peers
- Server/Client
Solution 2:
Mother-board
In personal computers, a motherboard is the central printed circuit board (PCB) in many modern computers and holds many of the crucial components of the system, providing connectors for other peripherals.
The first references I found are in 1956 to "mother" board, "mother-board" and "mother board"; the quotes suggest this is new terminology.
- EIA's 1956 Proceedings:
- IRE's 1956 International Convention Record, Volume 4, Part 2:
- Ziff-Davis's 1956 Popular Electronics, Volume 4, Issues 1-6:
- Hayden's 1956 Electronic Design, Volume 4, Part 2:
Baby-board
The observant will have noticed one of these early uses of mother-board are in conjunction with baby-board, and not today's common daughterboard. A mother-baby relationship seems more appropriate in this context than mother-daughter.
Daughter-board
A daughterboard, daughtercard or piggyback board is a circuit board meant to be an extension or "daughter" of a motherboard (or 'mainboard'), or occasionally of another card.
Daughterboard is the most common term nowadays. When did this replace baby-board?
The earliest I found was ten years later, in 1965 as daughter board, "motherboard-daughter board" and mother-daughter board.
- Hayden's 1965 Electronic Design, Volume 13, Part 3
- Rogers' 1965 Advances in Electronic Circuit Packaging:
- McGraw-Hill's 1965 Electronics, Volume 38:
Solution 3:
Mother lode and mother ship are older compounds along similar lines (both dating to at least 19th century, in mining and whaling respectively). Perhaps motherboard was coined by analogy with one of those? (Influence from mother ship seems very plausible, due to its sci-fi popularity.)
In each case, “mother X” seems to mean roughly “a big X, associated to some group of smaller X’s” — the metaphor seems fairly clear.
Unfortunately I can’t find any reliable sources right now with specific info on the origin of motherboard — hopefully someone else can, or I’ll try again tomorrow when I have OED access again…