The IEEE Standards Association (IEEE-SA) writes many standards, everything from “which symbols to use for units of measurement” (IEEE 260) to LANs (IEEE 802) to programming languages (IEEE 1178).
The standards are numbered more or less in sequential order. First they are assigned a project number; later that number is used for the resulting standard. See IEEE-SA Project Numbering Policy, which includes some exceptions such as joint projects with ISO, IEC, or JTC 1 which use five-digit numbers instead, or non-standard numbers that have “significant product recognition worldwide.”
So, IEEE 754 is more or less “the 754th standards-writing project started by IEEE-SA”. Its neighbor IEEE 753 is “Standard Functional Methods and Equipment for Measuring the Performance of Dial-Pulse (DP) Address Signaling Systems” (approved 1984) and its other neighbor IEEE 755 is “Trial-Use Extending High Level Language Implementations for Microprocessors” (1985, but now “withdrawn”.)
Originally answered on Quora: https://www.quora.com/Is-there-any-significance-of-754-in-the-name-of-IEEE-754-format-for-floating-point-representation/answer/Mark-Gritter